Topic: CX-12-84 cam experience?

[gschuld]

Does anyone here have experience with the big CycleX CX-12-84 cam?

It’s both high lift and long duration.  Lift matches the CX10 but with much longer advertised duration.

George

[Old Scrambler]

Very similar but slightly more aggressive than my custom Megacycle 125-x29. If you use that cam in a 300 head you will have to machine the valve pockets. At that lobe-distance you will have very little room to advance or retard the cam.

[MRieck]

You might be better off using the 32mm intake valve to get the valve to valve clearance. RC engineering did that with their large cams.

[gschuld]

Hmm.

Thanks Dennis. 

Mike, I didn’t know RC used 32 intakes on their biggest cams.  By biggest I assume you mean the RC454 cam?  .390/.390 lift with a huge duration rounded love shape.  That’s good to know as I have one of those cams.  The 32 intake might not be so bad with a forced induction or nitro engine.

But for naturally aspirated on race gas, using a 32 intake would seem to be going backwards.

My potential use would be for a 997cc to 1026cc high compression road race(maybe Bonneville once?) engine.

George

[NitroHunter]

In the 34mm intake F-2 head even the much milder RC 315 cam had valve-to-valve clearance issues, I was told strait out by RC that cam wouldn't work in that head. Reducing to 33.5 (Manleys) didn't make that much clearance difference except because being stainless and not stellite coated, they could be ground a little around the edge, then they quit hitting most of the time when you missed a shift. Man we thought we were so smart.

[MRieck]

Hmm.

Thanks Dennis. 

Mike, I didn’t know RC used 32 intakes on their biggest cams.  By biggest I assume you mean the RC454 cam?  .390/.390 lift with a huge duration rounded love shape.  That’s good to know as I have one of those cams.  The 32 intake might not be so bad with a forced induction or nitro engine.

But for naturally aspirated on race gas, using a 32 intake would seem to be going backwards.

My potential use would be for a 997cc to 1026cc high compression road race(maybe Bonneville once?) engine.

George

Not if you leave it open for 75% of the cycle.

[gschuld]

Yeah, yeah Mike.

So out of curiosity, were any of the naturally aspirated RC race engines using big cams and 32 intakes(like the early top gas bikes or the Vance and Hines double), of just the power added bikes(nitro counts)

For NA race engines, thee must be a trade off between larger valves and smaller cams and smaller valves and larger cams.  Then there is the variable of sinking the valves deeper, the deeper you go the more clearance you get, but at the sacrifice of chamber volume and stem height geometry issues at the rocker.

George

[Old Scrambler]

Consider smaller exhaust valves to gain overlap clearance.

Also consider that the actual opening and closing events may be a degree (or several) different from the spec on the cam-card.

[cbr954]

I just bought this cam and have it in my motor to check clearances.  Valve to valve had no issue in my RC head  33.5 intake stock exhaust.    Exhaust to piston clearance was fine, intake to piston was close....had .030" clearance.  Cam was degreed to the card specs.  Havent gotten any further on the build.   72mm MTC 12:1 pistons

[gschuld]

That’s positive news thanks…..

George

[bwaller]

Consider smaller exhaust valves to gain overlap clearance.

+1

[gschuld]

Yes shrinking the exhaust valve is a proven method. It will definitely be kept in mind.

George